Two-dimensional (2D) metals have long been known to display quasiparticle scattering of
a unique collinear character, arising due to
phase space constraints for scattering at the Fermi surface[1]}, [2]}. These collinear processes are generic and largely insensitive to the specifics of two-body interactions or the details of particle dispersion. The unique quasi-one-dimensional behavior arising from these processes endows the kinetics of 2D fermions with angular memory and gives rise to peculiar `tomographic' response effects[3]}, [4]}, [5]}. This behavior calls for a comparison with one-dimensional (1D) systems, where collinear scattering renders quasiparticles short-lived, destroying the Fermi-liquid state and replacing it with the Tomonaga-Luttinger state[6]}.
Below we argue that collinear processes in 2D metals take on a role which is a complete opposite of that in 1D liquids.
These processes give a giant boost to quasiparticle lifetimes and can be said to produce a “super-Fermi-liquid” that harbors a unique family of excitations with exceptionally long lifetimes, exceeding by orders of magnitude those familiar from Fermi-liquid theory.
